Electromagnetic relay



April 3, 1951 A. J. LEWUS 2,547,131

ELECTROMAGNETIC RELAY Filed Dec. 30, 1949 22 45 5 /43 3 SI M44 2 3| 0 25 42 51 59 so 5? 59 58 l 33 25 26 as as 272 I 293 255 250 2 2 s: 25? i 235 258 5? 256 .512) E 227 282 lnvenror Alexander J. Lewus y Q 6 l a. I V

Patented Apr. 3, 1951 UNITED STATES PATENT OFFICE ELECTROMAGNETIC RELAY Alexander J ay Lewus, Cicero, III.

Application December 30, 1949, Serial No. 1915;880

5 Claims. (01. 175-445) The present invention relates to electromagnetic relays, and more particularly to such relays of the current responsive or marginal type that are especially suited for use in the control circuits of single phase induction motors of the split phase or capacitor type.

A single phase induction motor of the type noted usually comprises a stator having a main or run winding and an auxiliary or start winding, and a squirrel cage rotor. In order to start a motor of this type the run and start windings are connected to an associated source of single phase alternating current; and thereafter, as the rotor approaches its full speed, the start winding is disconnected from the source. The ultimate acceleration of the rotor on into its full speed is accomplished by the run winding that is connected to the source. Subsequently, in order to arrest operation of the motor, the run winding is merely disconnected from the source.

One circuit control arrangement for a motor of the type noted comprises an electromagnetic relay of the current responsive or marginal type that is provided with a field structure carrying a winding, an associated movable armature, and switch contacts controlled by' the movements of the armature. The winding of the relay is con nected in series circuit relation with the run winding of themotor' across the terminals of the source; and the switch contacts of the relay are connected in series relation with the start winding of the motor across the terminals of the:

source; whereby the run winding and the startwinding of the motor are respectively connected and disconnected with respect to the terminals of the source, when the rotor of the motor is at rest. When the control circuit is initially closed a heavy current traverses the Winding of the relay and the series connected run winding of the motor, whereby the field structure of the relay attracts the armature effecting closure or" the switch contacts so that the start winding of the motor is connected across the terminals of the source. Thus the run winding and the start winding of the motor are connected in parallel circuit relationship with respect to each. other across the terminals of the source, whereby rotation of the rotor'of the motor is initiated. As tr e rotor of the motor is accelerated toward its full speed the current traversing the winding of the relay and the run winding of the motor is reduced due to the corresponding increased impedance of the run winding of the motor, since the motor has a predetermined impedance-speedcharacteristic, the. impedanceof; the run winding 2 increasing with speed of the rotor. being of the current responsive or marginal type, responds to the reduced current traversing the winding thereof and the series connected run winding of the motor; whereby this current becomes insufiicient to cause the field structure of the relay to retain the armature in its attracted position, when the rotor of the motor is accelerated toa predetermined speed toward its full speed. Thus, at this time, the armature of the relay is released by the associated fieldstructure eiiecting opening of the switch contacts so that the start winding of the motor is disconnected from across the terminals of the source.

It is immediately apparent that this circuit control arrangement for an electric motor of this type is satisfactory in operation only when the current responsive or marginal characteristic of the relay matches the impedance-speed characteristic of the motor fairly closely, whereby it is ordinarily necessary todesign a relay to match the particular impedance-speed characteristic of each variety of electric motor of this type.

Accordingly, it-is a general object of the pres ent invention to provide an electromagnetic relay of the current responsive or marginal type that incorporates an improved arrangement for varying the currentresponsive or marginal char acteristic thereof over a wide range, rendering the relay useful in control circuits for a wide variety of electric motors of the type noted.-

Another object of the invention is to provide in an electromagnetic relay, an improved: and simplified armature mounting and biasing arrangement.

A further object of the invention is to provide in an electromagnetic relay, an improved construction. and arrangement of the armature and contact actuating mechanism thereof.

A still further object of the invention is to provide an electromagnetic relay of rugged construction and arrangement that is eiiicient in operation and economical to manufacture.

Further features of the invention the particular arrangement of the elements of the electromagnetic relay, whereby the aboveoutlined and additional operating features of are attained.

The invention, both as to its organization? and method of operation, together with further ole-- jects and advantages thereof, will best be under-- stood by reference to the following specification,- taken in connection: with. the accompanying drawing in- Which- Figure 1 is an electric-diagram of a. control circuit for a single phase induction.

The relay, I

pertain to;

there- 3 motor of the split phase or capacitor type incorporating an electromagnetic relay embodying the present invention; Fig. 2 is a plan view of a relay embodying the present invention; Fig. 3 is an end view of the relay shown in Fig. 2; Fig. 4 is a vertical sectional view of the relay, taken in the direction of the arrows along the line 44 in Fig. 2; Fig. 5 is a fragmentary vertical sectional view of a modified form of the relay embodying the present invention; Fig. 6 is a vertical sectional view of another modified form of the relay embodying the present invention; and Fig. I is an enlarged exploded perspective View of a structural detail of the relay shown in Fig. 6.

Referring now to Fig. l of the drawing, there is illustrated diagrammatically an electric motor In of the single phase induction type that may comprise a split phase or capacitor type of operation, as well as a control circuit therefor inincluding an electromagnetic relay I l embodying the features of the present invention. The control circuit for the electric motor i is connected to a suitable source of single phase 60 cycle alternating current that may be of 110 volts by selectively controllable switching apparatus, not shown. Specifically, the electric motor l0 comprises a stator provided with a main or run winding l2 and an auxiliary or start winding l3, as well as a rotor M of the squirrel cage type. The relay ll comprises magnetic field structure including a core element carrying a winding and a movable armature operatively connected to an associated pair of contacts l5. The run winding l2 of the motor I0 and the winding of the relay H are connected in series circuit relation across the terminals of the control circuit; and the start winding [3 and the contacts are connected in series relation with an associated capacitor l5 and thence across the terminals. of the control circuit. The armature of the relay ll normally occupies its released position effecting opening of the contacts l5, whereby the start winding I3 is normally disconnected from across the terminals of the control circuit.

' order to start the motor In the associated switching apparatus is operated to its closed p0 sition'in order to effect energization of the run winding l2" of the motor Ill and the winding of the relay H. The relay ll, being of the current responsive or marginal type, attracts its armature closing the contacts l5, whereby the start winding I3 and the series connected capacitor [6 are bridged across the terminals of the control circuit. Thus at this time both the run winding l2 and the start winding l3 of the motor [0 are energized, whereby the circulating currents induced in the squirrel cage of the rotor l4 react with the magnetic fields produced by the windings l2 and i3 in order to initiate rotation of the rotor l4. As the rotor M is accelerated toward its full speed the current traversing the run winding l2 of the motor I0 and the winding of the relay II is reduced due to the increased impedance of the run winding l2 as a consequence of the rotation of the rotor M, the motor I0 having a predetermined impedancespeed characteristic. When the current traversing the run winding l2 of the motor Ill and the winding of the relay l l is reduced to a predetermined value, the field Structure of the relay H releases its armature opening the contacts I5,

whereby the start winding l3 of the motor In is disconnected from across the terminals of the control circuit. At this time the rotor 14 is accelerated on into its full speed by the run wind- 4 ing l2 alone. Subsequently, in order to arrest operation of the motor [0, the associated switching apparatus is operated to its open circuit position in order to de-energize the run winding l2.

In order to accommodate the electromagnetic relay llto a large variety of electric motors of the type noted, it is preferably of the construction and arrangement hereinafter described, whereby the current responsive or marginal characteristic of the relay ll may be adjusted or varied to match the impedance-speed characteristic of a wide variety of motors of the type noted.

Referring now to Figs. 2 to 4, inclusive, the electromagnetic relay 20 there illustrated and embodying the features of the present invention, comprises a supporting plate 2| formed of insulating material, such, for example, as Bakelite, and a substantially Z-shaped field element 22 formed of magnetic material and provided with a body 23 terminating in two oppositely directed arms 24 and 25. In the arrangement the arm 22 extends forwardly with respect to the adjacent lower end of the body 23, and the arm 25 extends rearwardly with respect to the adjacent upper end of the body 23. The arm 24 is suitably secured to the adjacent upper surface of the supporting plate 2i by an arrangement including a plurality of rivet eyelets 26 extending through aligned openings respectively provided in the plate 2i and in the arm 24. Also, a winding spool carrying element 21 formed of nonmagnetic material, such, for example, as aluminum, is carried by the adjacent upper surface of the arm 24 and secured in place by the eyelets 26 extending through aligned openings provided therein. The winding spool carrying element 21 comprises an upstanding substantially cylindricalbarrel 28 disposed forwardly with respect to the body 23 of the field element 22 and a lower substantially annular flange 29, the flange 29 being directly secured to the adjacent upper surface of the arm 24, as previously noted. Preferably, the barrel 28 of the element 21 has a longitudinally extending slit 30 formed therein in order to break the electrical circuit path around the barrel 28 so as to'minimize eddy currents in the barrel 23 that may be induced therein'when the winding provided on the associated winding spool is energized with alternating current.

Also, the relay 20 comprises a unitary winding spool and supported winding that is removably carried by the element 21, the heads of the winding spool being indicated at St and 32, and the winding being indicated at 33. The heads 3| and 32 of the winding spool are formed of insulating material, such, for example, as Bakelite, and the composite winding 33 is formed of suitable conducting wire, such, for example, as copper, or the like, the individual terminals of the composite winding 33 being suitably insulated from each other.

Aligned openings 3 and 35 are respectively formed in the plate 2| and in the arm 24, the openings 34 and 35 being arranged in alignment with the hollow barrel 28 of the element 2?. The opening 35 is threaded and engages the threaded exterior surface of a core element 36 projecting through the openings 34 and 35 and arranged within the barrel 28. The core element 36 is formed of magnetic material and the upper end thereof comprise'sa pole end terminating adjacent to the upper end of the barrel 28. It will be understood that the pole end of the core element 36 may be adjusted with respect to the upper end of the barrel 28 by virtue of the arrangement previously noted, the lower end of the core element 36 having a slot 31 formed therein that is adapted to receive a screwdriver, or the like, to facilitate the adjustments noted. Also, the lower end of the core element 36 carries a lock nut 38 so that the adjusted position of the core element 36 within the barrel 28 may be retained by virtue of the cooperation between the lock nut 38 and the adjacent lower surface of the plate 2|.

Further, the relay 2% comprises an armature 39 having a substantially Z-shape and including a body 40 terminating into oppositely directed arms 4| and 42. The arm 4| projects forward- 1y with respect to the associated upper end of the body 40 and constitutes the head of the armature 39 that cooperates with the associated pole end of the core element 38, while the arm 42 projects rearwardly from the associated lower end of the body 49 and constitutes the work lever of the armature 39. The armature 39 is formed of magnetic material and is pivotally mounted upon the upper portion of the body 23 of the field element 22 somewhat above the upper end of the barrel 23 and between the arms 24 and 25 of the field element 22. Specifically, a substantially centrally disposed opening 43 is formed in the upper portion of the field element 22 at the junction between the upper end of the body 23 and the arm 25, whereby two spacedapart sides 44 and 45 extend between the upper end of the body 23 and the rear extremity of the arm 25. Further, two side notches 4t and 4'! are respectively provided in the sides and 45 adjacent to the bottom of the opening 43 that respectively receive two tabs 48 and 49 provided on the opposite sides'of the armature 39 ad jacent to the junction between the body :39 and the head 4| thereof. Thus, it will be understood that the arrangement, comprising the side notches 46 and 47 respectively provided in the lower portions of the sides 44 and 45 and merge ing into the opening 43 and respectively receiving the tabs 46 and 4'! provided on the armature 39, mounts the armature 39 upon the field element 22 for pivotal movements, the head ii of the armature 39 being selectively movable toward and away from the pole end of the core element 36 about the tabs 48 and 49 respectively riding in the side notches 46 and 4'1.

The armature 39 is normally biased in its released position illustrated by an arrangement comprising a tension element or spring 55 projecting through the opening 43 and cooperating between the front end of the head 4| and a screw More particularly, a substantially centrally disposed slot 52 is provided in the front end of the head 4| of the armature 39 that receives the front end of the spring 59, the front end of the spring 59 being arranged in the slot 52 and hooked over the lower surface of the head 4|. The rear end of the arm 25 is curved first downwardly and then rearwardly and comprises a knockout tab 53 that is disposed above the extreme rear end of the arm 25, the screw 5i extending between the tab 53 and the extreme rear end of the arm 25 and receiving the rear end of the spring 59, the rear end of the spring 59 being provided with a hook engaging the threaded body 01 the screw 5|.

As described above, the front end of the tension element 50 is pivotally connected to the front end of the head 4| in the slot 52, while the rear end of the tension element 59 is connected to the threaded body of the screw 5|. Thus, it will lective movements of the rear end of the tension.

element 50 up and down with respect to the front end thereof. Accordingly, the tension element 50 normally biases the armature 39 in the counterclockwise direction, as viewed in Fig. 4, about the pivotal mounting, including the tabs 48 and 49 riding in the cooperating side notches 46 and 41; and the moment of this bias exerted by the tension element 59 upon the front or free end of the head 4| is selectively varied or adjusted depending upon the position of the rear end of the tension element 50 upon the associated screw 5|. Specifically, it will be appreciated that as the rear end of the tension element 50 is moved downwardly away from the tab 53 the angle between the tension element 59 and the head 4| is decreased, whereby the effective moment of the bias exerted by the tension element 59 upon the armature 39 is correspondingly decreased.

Recapitulating, it will be understood that with a given pull between the ends of the tension element 56 the effective moment of this pull that is exerted upon the armature 39 may be varied by varying the angle between the tension element 56 and the head 4| of the armature '39; which may be accomplished merely by appropriate adjustment of the screw 5 i. Finally, a lock or set screw 54 is placed in a threaded opening provided in the tab 53 and arranged in cooperating relation with respect to the head of the screw 5| so that the adjusted position of the screw 5| may be preserved.

In view of the previous description of the arrangement for adjusting the position of the core element 36 with respect to the end of the barrel 28 and consequently with respect to the head 4| of the armature 39, it will be understood that the magnetic reluctance of the field structure including the field element 22 and the. core element 3B, and the armature 39 may be readily adjusted. The combination of the adjustment of the bias upon the armature 39 and the adjustment of the magnetic reluctance of the field structure permits a composite variation of the current responsive or marginal characteristic of the relay 29 over a wide range; whereby the relay 20 may be employed in the control circuits of a wide variety of the electric motors of the type noted. In other words, the characteristic of the relay 29 may be adjusted over a wide range in order to match it to the impedance-speed characteristic of a particular electric motor, the composite adjustment being obtained by the flexibility of the factors previously noted.

Finally, the relay 2e comprises a stationary switch spring 55 and a movable switch spring 55, both suitably mounted upon the plate 2| and insulated from each other. The switch springs 55 and 56 are formed of suitable electrical conducting material and preferably the movable switch spring 56 comprises considerable resiliency. lhe

= switch springs 55 and 55 respectively carry stationary and movable contacts 57 and 58 that may be formed of precious metal for the purpose of making and breaking the electrical circuit between the switch springs 55 and 56. Further, the switch spring 56 carries a pair of oppositely disposed upstanding arms 59 carrying a pin 60 extending therebetween upon which an insulating roller or bead 5| is mounted. The roller 6| may be formed of glass, or the like, and is readily rotatable upon the pin 66 in order to eliminate friction therebetween. The outer surface of the roller BI is urged by the resiliency of the movable switch spring 56 into engagement with the adjacent lower surface of the work lever 42 of the armature 39.,

When the armature 39 occupies its normal released position illustrated in Fig. 4, the work lever 42 engaging the outer surface of the roller 6i retrains the switch Spring 55 in its lower position so that the contacts 51 and 58 are disengaged. When the armature 39 is moved into its attracted position with respect to the adjacent end of the barrel 28, it is pivoted in the clockwise direction, as viewed in Fig. 4, whereby the work lever 52 is effectively moved away from the pin 60 so that the outer surface of the roller BI rolls upon the adjacent surface of the work lever 42 as the roller 6! follows=the work lever 52 as a result of the resiliency of the switch spring 56, whereby the contact 58 is moved into engagement with the contact closing the electric circuit between the switch springs 55 and 56. Subsequently, when the armature 39 is returned to its normal released position, as illustrated in Fig. 4,

the work end of the lever 42 engaging the adjacent surface of the roller 5i forces the roller BI, as well as the pin 52 and the switch spring 56 downwardly, the outer surface of the roller GI rolling upon the adjacent lower surface of the work lever 42, whereby the movable contact 53 again disengages the stationary contact 52 in order to open the electric circuit between the switch springs 55 and 56. This contact actuating mechanism including the roller SI is very advantageous in view of the fact that a minimum amount of friction is involved in the transfer of motion between the work lever E2 and the movable switch spring 55.

It will be understood that the critical current that must traverse the winding 33 in order to effect movement of the armature 39 from its released position into its attracted position, as well as the critical current that must traverse the winding 33 in order to retain the armature 59 in its attracted position after it has been operated thereto, may be selectively adjusted, first by adjustment of the magnetic reluctance of the field structure including the core element 35, and second by adjustment of the moment of the bias of the tension eiement 50. Further, this current responsive or marginal characteristic may be adjusted externally thereof by providing a variable shunt circuit, not shown, bridging the terminals of the winding 33.

Referring now to Fig. 5 of the drawing, the modified form of the relay E there illustrated, and embodying the features of the present invention, comprises the essential construction of the relay 22, previously described. However, in this modification the arrangement for adjusting the moment'of the bias applied by the tension element I55 between the front or free end of the armature I and the screw I5I comprises a nut III that is threaded upon the body of the screw I5I and is suitably attached to the rear end of the tension element I55. In this arrangement the nut III projects into an opening 5'52 provided in the rear end of the arm I25 in order positively to prevent rotation of the nut III incident to its travel along the body of the screw I5i. This arrangement accomplishes the same general function as the corresponding arrangement incorporated in the relay 25 with regard to-adjusting the moment of the bias applied to the armature I39.

Also, in the relay I20 there is incorporated a resilient buffer IBI projecting through an opening provided in the extreme rear end of the arm I25, the buffer I3! being mounted for sliding movement in the opening provided in the rear end of the arm I25 and cooperating with the extreme rear end of the work lever I22 of the armature I39. This arrangement further comprises an adjustable screw E62 arranged in a threaded opening formed in the tab I53, and a compresthrough the compression spring I83 upon the buffer I8I, the rear end of the work lever I42 striking the adjacent end of the buffer I8! when the armature I39 is moved into its attracted position with respect to the associated core element, not shown. useful in adjusting the critical current that must .be maintained in the winding I33 of the relay I20 in order to retain the armature I39 in its attracted position after it has been operated thereto.

Referring now to Figs. 6 and '7, the other modified form of the relay 226 there illustrated, and embodying the features of the present invention, comprises the essential construction of the relay 22, previously described. However, in this modification the arrangement for adjusting the bias that is applied by the tension element 250 to the front or free end of the armature 239 comprises a simple threaded element 21% projecting through an associated opening 2'52 provided in the rear end of the arm 225 of the field element 222, and a cooperating nut 213. In this arrangement the tension in the spring 252 is directly adjusted by the position of the nut 273 upon the threaded element 2'H.

Also, in the relay 220 the movable contact spring 256 not only cooperates with the stationary contact spring 255, but also with a stationary contact 28E. Specifically, the movable contact spring 256 carries the front contact 258 that cooperates with the front contact 25? that is carried by the fixed contact spring 255, as well as a; back contact 282 that cooperates with the fixed back contact 28H. Thus in the relay 220 two electric circuits may be alternately opened and closed by the respective contact pairs 25?, 258 and 28!, 282.

Finally, in the relay 225 the upper end of the barrel 228 of the winding spool carrying element 221 is inwardly flanged and receives a removable pole piece or button 2% that directly cooperates with the head 24I of the armature 239. In this arrangement the pole piece or button ZSI is formed of magnetic material and is provided with a surrounding slot 292 that directly engages the inwardly flanged upper end of the barrel 228, the slot 235 formed in the barrel 228 lending sufficient resiliency to the connection to facilitate ready placement and removal of the button 29I from the front end thereof. In order further to minimize chattering of the head 2M of the armature 239 with respect to the pole piece 29I a low resistance shunting winding 253 formed of copper, or the like, is inductively coupled to one portion or leg of the pole piece 25! defined by a slot 294 formed therein. The low resistance winding 293 comprises a continuous ring and serves the usual purpose of conducting eddy current there in in order to obtain a slight phase shift between the magnetic flux in the two portions or le s of This arrangement is particularly the field piece 29! disposed on opposite sides of the slot 294, whereby chattering of the armature 239 is eliminated, when the winding 233 is ener gized with alternating current.

In view of the foregoing it is apparent that there has been provided an electromagnetic relay incorporating improved structure for varying the current responsive or marginal characteristic thereof over a wide range, thereby lending flexibility to the relay for use in the control circuits of a wide variety of single phase induction motors of the split phase or capacitor type.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. An electromagnetic relay comprising a substantially Z-shaped field element providing an upstanding body and a lower forwardly extending arm and an upper rearwardly extending arm, an upstanding core element secured to said forwardly extending arm and provided with a pole end terminating below said rearwardly extending arm, a winding carried by said core element, an armature, a pivotal connection between said armature and said body, said armature having a forwardly extending free end disposed above said pole end of said core element and being movable toward and away from said pole end of said core element about said pivotal connection, said body having a hole formed therein and disposed above said pivotal connection, a tension element disposed above said armature and projecting through said hole, a rotatable member carried by said rearwardly extending arm, one end of said tension element being connected to said member and the other end of said tension element being connected to said free end of said armature so that said tension element normally biases said free end of said armature away from said pole end of said core element about said pivotal connection, and means controlled by rotation of said member for selectively adjusting the position of said one end of said tension element different distances above said pivotal connection in order selectively to vary the moment of the bias exerted by said tension element upon said free end of said armature.

2. An electromagnetic relay comprising a substantially Z-shaped field element providing an upstanding body and a lower forwardly extending arm and an upper rearwardly extending arm, an upstanding core element secured to said forwardly extending arm and provided with a pole end terminating below said rearwardly extending arm, a winding carried by said core element, said body having an opening formed therein, an armature, a pivotal connection between the intermediate portion of said armature and said body within said opening so that one end of said armature extends forwardly and the other end of said armature extends rearwardly with respect to said body, said one end of said armature constituting a free end disposed above said pole end of said core element and being movable toward and away from said pole end of said core element about said pivotal connection and said other end of said armature constituting a movable work element, said body having a hole formed therein and disposed above said pivotal connection, a tension element disposed above said armature and projecting through said hole, a rotatable member carried by said rearwardly extending arm, one end of said tension element'being connected to said member and the other end of said tension element being connected to said free end of said armature so that said tension element normally biases said free end of said armature away from said pole end of said core element about said pivotal comiection, and means controlled by rotation of said member for selectively adjusting the position of said one end of said tension element different distances above said pivotal connection in order selectively to vary the moment of the bias exerted by said tension element upon said free end of said armature.

3. The electromagnetic relay set forth in claim 2, wherein a resilient element is arranged in cooperating relation with said work element, and a roller is mounted upon said resilient element and is forced thereby into rolling engagement with said work element.

4. The electromagnetic relay set forth in claim 1, wherein said core element projects through an aperture provided in said forwardly extending arm and is adjustable with respect thereto in order to effect adjustment of said pole end of said core element toward any away from said free end of said armature.

5. The electromagnetic relay set forth in claim 2, wherein said armature is substantially Z- shaped so that said free end of said armature and said work element comprise arms thereof respectively disposed above and below said pivotal connection.

ALEXANDER JAY LEWUS.

REFERENCES CITED The following references are of record in the file of this patent:

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